7 August 1998

Soya improves urea gains

By Simon Wragg

INITIAL trials at SACs Bush Estate, Edinburgh, using urea-treated wheat as a low cost feed which needs no processing proved disappointing last year. Continen-tal cross steers in the trial achieved daily liveweight gains of just 1.1kg/head.

However, SAC nutritionist Mitch Lewis says new trials supplementing urea treated wheat with small amounts of soya have significantly improved liveweight gains. "Final results show live-weight gains of 1.28kg/head/day over a 125-day period when supplemented with 5% soya," he says.

Aiming to remove the need for processing grain, urea is added to wheat harvested at 30% moisture using a simple nozzle applicator connected to a grain auger emptying into a conventional bin. Treated grain is stored in the bin, covered in plastic and left to ferment.

If grain is too moist, above 35-40%, Mr Lewis warns that it can ferment before treatment, turning acidic and jeopardising the successful conversion of urea to ammonia.

With this years late harvest producers still have the opportunity to cut wheat crops at 30% moisture to produce a low cost feed rather than trying to harvest crops that have lodged and may not dry out anyway, says Mr Lewis.

"The urea treatment costs about £10/t DM, compared to £15.20/t DM – including contractors charges – for crimped wheat treated with a commercial product," he says.

A 3% urea treated wheat feeds out at about 16-18% protein and ensures ammonia is generated during storage to break down the seed coat, explains Mr Lewis. But poor trials results last year led SAC nutritionists to supplement the urea treated wheat with either soya or molasses.

"We thought molasses might trap the ammonia and improve performance, but the small increase in liveweight proved it not worthwhile. But adding soya at 5% gives a lift in liveweight gain of about 0.2kg/ head/day," he adds.

How the soya boosts performance in unknown, says Mr Lewis. "We think it acts in the rumen rather than as digestible undegradable protein later on."

Cost/kg gain has improved, falling from 65p for steers fed urea treated wheat to 59p for steers fed urea treated wheat supplemented with soya.

"There may be some benefit to feeding the ration to medium performance dairy cows," he says. High yielders, typically those producing 40l/day, would not benefit because rumen throughput would be too high to allow adequate digestion, Mr Lewis adds. &#42

UREATREATEDWHEAT

&#8226 Boosts DLWG from 1.1 to 1.3kg/head.

&#8226 Lowers cost/kg gain from 65p to 59p/kg.

&#8226 Medium yielding dairy cows could also benefit.

SAC nutritionist Mitch Lewis says urea treated wheat and soya can help achieve daily liveweight gains of 1.3kg/head.